With all the contradictory claims made these days about the healthbenefits of low-fat diets, the harm of hormone replacements and thedangers of pain relievers, at least we still know that a drink or twoa day is good for the heart.

Well, maybe not.

Researchers at UCSF pored through more than 30 years of studies thatseem to show health benefits from moderate alcohol consumption, andconcluded in a report released today that nearly all contained afundamental error that skewed the results.

That error may have led to an erroneous conclusion that moderatedrinkers were healthier than lifelong abstainers. Typically, studiessuggest that abstainers run a 25 percent higher risk of coronary heartdisease.

Without the error, the analyses shows, the health outcomes formoderate drinkers and non-drinkers were about the same.

"This reopens the debate about the validity of the findings of aprotective effect for moderate drinkers, and it suggests that studiesin the future be better designed to take this potential error intoaccount,'' said Kaye Fillmore, a sociologist at the UCSF School ofNursing and lead author of the study.

The common error was to lump into the group of "abstainers" people whowere once drinkers but had quit.

Many former drinkers are people who stopped consuming alcohol becauseof advancing age or poor health. Including them in the "abstainer"group made the entire category of non-drinkers seem less healthy incomparison.

This type of error in alcohol studies was first spotted by Britishresearcher Dr. Gerry Shaper in 1988, but the new analysis appears toshow that the problem has persisted.

Fillmore and colleagues from the University of Victoria, BritishColumbia; and Curtin University, in Perth, Australia, analyzed 54different studies examining the relationship between light to moderatedrinking and health. Of these, only seven did not inappropriatelymingle former drinkers and abstainers.

All seven of those studies found no significant differences in thehealth of those who drank -- or previously drank -- and those whonever touched the stuff. The remaining 47 studies represent the bodyof research that has led to a general scientific consensus thatmoderate drinking has a health benefit.

Fillmore's team of researchers took their initial finding one stepfurther, and introduced the error into the data compiled in the sevenstudies and, voila, the results changed to show drinkers had betterhealth than abstainers.

The UCSF study appears today in an online edition of the journalAddiction Research and Theory.

Kaiser Permanente cardiologist Dr. Arthur Klatsky, who led some of thelargest studies showing a protective effect for moderate alcoholconsumption, said his first study in 1981 contained the flaw, butsubsequent studies took it into consideration.

"Without question, it is a serious flaw, which we have readilyadmitted,'' he said. He contends, however, that Fillmore's analysismistakenly attributes the same mistake to later research.

"The evidence is still pretty compelling that there are likely to bebenefits'' from moderate drinking, he said. In addition, he said,studies show that alcohol raises the level of HDL -- the so-calledgood cholesterol -- and also has anti-clotting effects, which canreduce the risk of heart attack.

Klatsky said that there are inherent weaknesses in all theepidemiological studies of alcohol and heart health. What is needed,he said, is a randomized trial in which a group is assigned to consumeone or two drinks a day and another abstains, and their comparativehealth is assessed over a period of years.

Dr. Tim Naimi, a physician who works for the National Center forChronic Disease at the Centers for Disease Control and Prevention inAtlanta, said "the whole field of 'moderate drinking' studies isdeeply flawed,'' because of the lack of randomized trials.

In a study published in May 2005 in the American Journal of PreventiveMedicine, Naimi and other CDC colleagues found that the comparativelyhigher risk of heart disease in abstainers could be explained bysocioeconomic factors rather than lack of protection from alcoholconsumption.

Non-drinkers, for example, tended to be poorer than drinkers, had lessaccess to health care, and had less healthy diets.

"Anyone who suggests that people should begin drinking, or drink morefrequently, to reduce the risk of heart disease is misguided,'' hesaid.